The Chemistry of Life The Nature of Matter

Chemistry Life depends on chemistry. The study of chemistry begins with the basic unit of matter, the atom.

Atom The atom is made up of three subatomic particles: Protons Neutrons Electrons

Protons and Neutrons Protons are positively charged particles. Neutrons carry no charge. Strong forces bind protons and neutrons together to form the nucleus, which is at the center of the atom.

Electrons Electrons are negatively charged particles. Electrons are found in a cloud outside of the nucleus. We describe them as being in shells. Because atoms are neutral, the number of electrons equal the number of protons.

Electron Shells First shell: called K – 2 electrons Second shell: called L – 8 electrons Third shell: called M – 18 electrons Fourth shell: called N – 32 electrons Fifth shell: called O – 50 electrons

Elements A chemical element is a pure substance that consists entirely of one type of atom. 92 Elements exist naturally. We classify elements based on electrons in the outer shell, and organize them into a chart called the Periodic Table of Elements.

The Periodic Table of Elements

Reading the PToE Element Symbol Element Name 6 C Carbon 12.011

Reading the PToE Atomic Number: the number of protons in the atom. 6 Mass Number: the sum of the protons and neutrons in the nucleus Atomic Mass: the average of the mass of the isotopes 6 C Carbon 12.011

Isotopes Atoms of the same elements that differ in the number of neutrons they contain are known as isotopes. Because the have the same number of electrons, all isotopes of an element had the same chemical properties.

Isotopes of Carbon

The Atom’s Family e e e Nucleus Electron Shells e e e